PHILOSOPHICAL 
TRANSACTIONS 
OP THE 
ROYAL SOCIETY OF LONDON. 
Series A. 
CONTAINING PAPERS OF A MATHEMATICAL OR PHYSICAL CHARACTER. 
VOL. 218. 
Printed and Published for the ROYAL SOCIETY by 
HARRISON AND SONS, 44-47, ST. MARTIN’S LANE, LONDON, W.C. 2, 
printers in @rbinarg to pis |$lajestg. 
July - , 1919. 
